Nick, police do have security video they're now studying. What more can you tell us?

NICK PATON WALSH, CNN SENIOR INTERNATIONAL CORRESPONDENT: That's right, Wolf. They're trying to piece together a timeline of exactly what happened between about 1:00 and 4:00 local time on Sunday afternoon, when Sergei Skripal and his daughter, Yulia, who is visiting from Russia, were found slowly falling unconscious on a quiet bench near a shopping center, a mall, in the rural city of Salisbury. But the bombshell, frankly, we've heard behind me here takes that instance to a whole new international level. The top counterterrorism police officer for the United Kingdom, Assistant Commissioner Mark Rowley, saying that they believe this is attempted murder through the administering of a nerve agent.

They've gone on to say that they specifically know what that nerve agent was. They're not publicly identifying it. Wolf, as you know, that narrows down enormously, potentially, who could have supplied a chemical like that. VX, Sarin, two well-known ones. But only a small number of countries own those.

They went on to say here that those two individuals were deliberately targeted in this specific attack. They are putting together a closed- circuit television timeline of events around there. They're appealing for information.

They went on to say that one of a number of first responders who went to the scene there, a police officer, is still seriously ill from that nerve agent. So, we have three people still in hospital here.

But there are a lot of questions not answered here, purposefully, frankly, given the ongoing investigation. Who administered that particular poison? Where did it happen?

We know that an Italian pizza restaurant and a pub, a bar nearby called the Bishop's Mill, are still sealed off by police, still being pored over. And the area around there, of course. They're trying to work out exactly where it was they went and where this could have been administered.

But step back and listen to exactly what we're dealing with here. A former Russian foreign intelligence officer convicted in 2006 is given 13 years in a Russian jail for working for Britain's MI6 intelligence agency.

Swapped in 2010 for part of an exchange of four Russians held in Russian jails. Swapped -- they were all thought to be foreign agents. Swapped for Russians held by the United States accused of espionage, including Ana Chapman, if you remember that particular notorious name.

He, then, chose to live his life out in Salisbury, in that quiet town. His wife died sadly. His son died, sadly, too, in recent years. Yulia came to visit. It seems quite close, in fact, to the birthday of Alexander, his son.

And, at this stage, they are still trying to work out precisely who it was who delivered that particular poison and who they were working for. All fingers, sadly, at this point, and quite troubling here in London, near Westminster, pointing towards Moscow -- Wolf.

BLITZER: And this Russian double agent, Sergei Skripal, his daughter, Yulia, how are they doing? Are they still in the hospital?

WALSH: Yes, they are still in the hospital. They are still critically ill. Of course, their condition is paramount concern. Also, any testimony they can provide. They are, of course, the key witnesses here, if they're able to explain when they began to feel ill.

They will, of course, be looking to see if there are any third party here who may have administered the poison. This is not something you could necessarily just leave lying in wait for somebody. That's a key part of the situation here.

But, Wolf, remember, this is not the first time. Remember, back in 2006, a former Russian spy, Alexander Litvinenko, he was killed, murdered by Polonium, the radiative poison which could only be supplied by a state, too. Immediately traced back to Russia.

[13:05:02] People will be asking, why were fingerprints on this nerve agent so clearly left? Why is it so obviously going to lead back to a small number of countries who could ultimately be responsible?

And over there in the British house of commons of parliament, there will be enormous pressure now to respond authoritatively toward Russia or whoever is ultimately found to be to blame for this -- Wolf.

BLITZER: Nick Paton Walsh on the scene for us at Scotland Yard. We'll get back to you.

Very, very intriguing. Very disturbing developments, indeed.

There are other important stories we're following right now. And turning to the apparently irreconcilable differences over at the White House and the resignation of a key adviser to President Trump. Top economic adviser Gary Cohn is out.

The president ignoring Cohn's advice on controversial trade tariffs. But don't call it chaos in the west wing. The president says it's just the way he actually likes things to work with a very healthy dose of conflict.

Let's go to our Chief White House Correspondent Jim Acosta.

Jim, the turmoil continues. Have we heard anything today from the White House?

JIM ACOSTA, CNN CHIEF WHITE HOUSE CORRESPONDENT: A little bit, yes, Wolf. Earlier this morning, Sarah Sanders, the White House Press Secretary, held a brief gaggle with reporters and essentially said, you know, look at the record of this administration. This is not chaos.

But, of course, she was talking about policy and foreign policy issues, not exactly the staff turmoil that's going on inside the west wing, which we've seen unfold week after week after week.

And this week's episode is the departure of Gary Cohn, the president's top economic adviser. You know, essentially, what the White House is trying to do, at this point, is minimize the magnitude of Cohn's departure, even though there are some Republicans and top Republicans up on Capitol Hill who are lamenting all of this. Democrats are latching onto this as well, sensing an issue. Here's what the Senate minority leader, Chuck Schumer, had to say about this earlier today.

(BEGIN VIDEO CLIP)

SEN. CHUCK SCHUMER (D), NEW YORK, SENATE MINORITY LEADER: The problems here is the White House is getting hollowed out and the number of people capable of doing things, doing real things, whether you agree or disagree ideologically, is getting smaller and smaller. And they seem unable to recruit new people to take these jobs.

So, the kind of mess-ups we've seen this past week, I think, we're going to see over and over and over again. The president's erratic style. I didn't vote for Jeff Sessions, but I think it's a symbol to everybody what he did to his best friend, Jeff Sessions is don't go work there.

And I have heard story after story of capable people in the Gary Cohn mold, being -- trying to be recruited by the White House and no one wants to go.

(END VIDEO CLIP)

ACOSTA: Now, speaking of people being recruited by the White House, the White House is acknowledging the fact that they are starting to consider some replacements for Gary Cohn. Larry Kudlow, the Analyst on CNBC, is said to be among the top names on the president's list for his chief economic advisor.

The president likes to watch people on T.V. And Larry Kudlow is somebody he likes to watch on T.V. So, that certainly means that he's probably pretty high on the president's list.

But, Wolf, keep in mind, over here at the White House, and I think we'll hear this this afternoon, potentially at the briefing with Sarah Sanders at 2:30. They're trying to minimize the importance of Gary Cohn's departure.

Last night, I talked to a source close to the White House who said that west wing officials were, essentially, brushing off Cohn's departure, saying he was a New York guy, going back to New York. Sort of lumping him in with Hope Hicks and Josh Raffel, the Spokesperson for Jared Kushner and Ivanka Trump, as New York people who go back to New York.

Wolf, west wing officials may have been neglecting to mention when they were saying that to this source outside the White House for us in their spinning -- their attempt to spin all of this, that the president is from New York. I suppose New York people do go back to New York, but they probably don't want the president to go back that quickly, Wolf. Another sign of the chaos here at the White House.

BLITZER: President Trump certainly is a New York guy, himself. Originally from Queens but lived in Manhattan for most of his life.

All right, thanks very much for that, Jim Acosta.

Gary Cohn is the most recent high-profile departure from the Trump White House, but he's certainly not the first.

I want to go to CNN Politics Reporter and Editor at Large Chris Cillizza. He's over at the magic wall for us.

Chris, walk us through this rather unusual amount of White House turnover and unusual amount of feuding.

CHRIS CILLIZZA, CNN POLITCS REPORTER AND EDITOR AT LARGE: Yes, Wolf, I think that's the most important thing to start with. This is not normal. You're talking about almost four dozen senior staffers throughout the administration.

Now, if you look at -- we bare -- it's lucky the magic wall is big because we could barely fit them all.

So, there's lots of people, some you've heard of, some you haven't. But, remember, it's not just the number of departures, Wolf, it's who.

Mike Flynn, the National Security Adviser; Reince Priebus, the Chief of Staff; Anthony Scaramucci, the Communications Director. I feel like we could probably have one line of just communications directors who have left.

Steve Bannon, the White House Counselor. Over and over. Sean Spicer, another Communications Director.

And then, you know, Gary Cohn, the National Economic Adviser. Over and over again. People who have left. Obviously, you have Katie Walsh, for example, a Deputy Chief of Staff, who left.

You have James Comey who didn't leave of his own volition. But over and over again, you see high-level, senior people leaving.

Reminder as you look at this, Donald Trump has been in office for a little over 13 months.

[13:10:02] Let's go to the next one, because it's not just about the people who have left.

OK. So, these are active feuds the president is currently engaged in. Now, you'll notice, all these people are members of his administration that he's feuding with. These are active feuds. So, H.R. McMaster, Trump has run down in private. He's fought with Rex Tillerson, the Secretary of State. Rumors, literally every week, that Tillerson might leave.

Jeff Sessions, we know. What name hasn't he called Jeff Sessions? Beleaguered, disgraceful, says he's not focused on things. Chris Wray, who, by the way, was the replacement for Jim Comey that Donald Trump chose. And Rod Rosenstein, the Deputy Attorney General, Trump has made no secret of his dislike.

Let's go to one more slide. And this one, I think, will really get you. Now, this is just people who he may not be actively feuding with but that have issues of their own.

I think these are the two, really, to pay the most attention to. Jared Kushner and Ivanka Trump are two of the people closest to Donald Trump in his orbit. Obviously, his son-in-law and his daughter.

Jared Kushner, any number of issues, most notably on security clearances. Still doesn't have a permanent security clearance, dealing with only a secret, not a top-secret security clearance.

And then, I mean, down here, these are cabinet officials. So, Scott Pruitt at EPA, Shulkin at Veterans, Zinke at Interior, Ben Carson at Hud. Pick -- sort of a pick who you want. Ben Carson spends $13,000 on a dining set for his office at Hud. Must be a nice dining set. They canceled that.

Zinke, any number of issues. Shulkin, spending money on a trip to Europe with his wife. Misuse of taxpayer funds. Inspector general's report pending.

So, there's a -- Don McGahn in the middle of all the Russia stuff as White House counsel.

So, it's not just the departures. It's not just the feuds with this administration. It's also -- this is a who's who of about half of Donald Trump's most relied upon allies. They are struggling on their own.

So, it's not a staff issue. It's a can you get things done amid all this controversy? And I know Donald Trump doesn't like to hear the word, Wolf, but all this chaos.

BLITZER: It certainly is chaotic over there. All right, thanks very much. Chris Cillizza with that report.

Juana, what do you make of Gary Cohn's departure? What it means for a possible trade war? But also, what it means for the chaos inside the White House?

JUANA SUMMERS, CNN POLITICS SENIOR WRITER: Sure, it's just the latest chapter, as Chris Cillizza was noting, of this rapid string of departures. And I think this certainly shows some concern on Wall Street about what Gary Cohn's departure means.

He was seen, particularly among Republicans, as somebody who was a, kind of, steady force in the White House in this very important economic position. Someone who could keep the president from the brink of starting what he said is a trade war. Something he said in a tweet last week that might actually be a good thing. His economic views have been a sharp contrast for this president.

So, I think there is a lot of concern as to what could come next and what this could mean for economic futures. And I think we saw the markets respond to that as that news was announced yesterday. BLITZER: The markets were not very happy about that. Peter Navarro, he's rumored to be in line, potentially, to take over that position. He's more like the president, a protectionist, as opposed to a free trader.

MOLLY BALL, CNN POLITICAL ANALYST: That's right. And unlike a lot of the other feuds that the president has had, this one is actually a policy dispute. This is about different ideological factions in the White House. The president, as you said, has always had protectionist impulses.

And it was, really, the centerpiece of his campaign. It differentiated him from all of the other Republican candidates in the primary, and then from Hillary Clinton in the general election, that he was adamant about enacting tariffs to make America stronger in the world market. And to combat the influence of China as he perceived it.

He brought in some very unorthodox -- people with unorthodox economic views, notably Peter Navarro and Robert Lighthizer and Wilbur Ross, the Secretary of Commerce. But they have been -- they have been held at bay by people like Gary Cohn, who are the same page as Republicans in Congress who really don't want any, kind of, protectionism, who really believe in free trade and free markets.

Now, Gary Cohn appears to be signaling that he's lost that fight. Even though the tariffs haven't -- the paperwork hasn't yet been signed on the tariffs. There's still a pressure campaign to get the president not to go through with it. But Cohn appears to be giving up the ghost.

BLITZER: Here's what the president said about all the fighting -- the infighting that's going on right now. Listen to this, Juana.

(BEGIN VICDEO CLIP)

DONALD TRUMP, PRESIDENT OF THE UNITED STATES: I like conflict. I like having two people with different points of view. And I certainly have that. Then I make a decision. But I like watching it. I like seeing it. And I think it's the best way to go. I like different points of view.

(END VIDEO CLIP)

BLITZER: How's that working out?

SUMMERS: Not very well, clearly. I think, you know, the president doesn't like to call it chaos, but the fact of the matter is that people have been departing, either by their own volition or being pushed out by the president and his top aides of this White House at an unprecedented pace.

And I think we simply can't ignore that, from a policy standpoint, as Molly notes with Gary Cohn's departure. And from a political standpoint, in terms of the president is pushing away people who fundamentally disagree with him. This is a president who we know prizes loyalty among -- above everything else.

[13:15:00] He is someone who wants to keep close people who agree with him, who support him, who he has seen support. And I think that's why these departures are so important for us to keep tracking.

BLITZER: Hope Hicks, the communications director, long-time aide to the president, announces she's gone last week. Now Gary Cohn. More are on the way. There's no doubt about that.

BALL: Probably. I mean there does seem to be an expiration date for anybody working in this White House, in part because it's a stressful place to work. It's a high-pressure place to work. The kind of conflict that Trump is talking about can be productive if you think of the idea of a team of rivals, like Abraham Lincoln famously had. But it wears on people when it is so acrimonious.

And when the president seems to pit people against each other and enjoy it almost as if he's sort of watching a cage match, people get tired of that, or the president gets tired of them and they eventually decide that the grass is greener on the other side of those White House doors.

BLITZER: Let's see what happens to General H.R. McMaster, the national security adviser, in the coming days, and John Kelly, the White House chief of staff, as well, among others. Everyone is watching.

Guys, thanks very, very much.

A porn star suing the president of the United States. Why a missing signature on a hush agreement may be what exposes the alleged affair.

Plus, fresh off a security clearance downgrade, Jared Kushner is abroad, he's meeting with Mexico's president as tensions escalate.

And he's a Middle East specialist with deep ties to the president's inner circle. And now he's cooperating with the special counsel, Robert Mueller. An explosive development. We have details. Stay with us.

(COMMERCIAL BREAK)

[13:20:35] BLITZER: A porn star who claims to have had an affair with President Trump before he ran for office and accepted $130,000 for her to stay quiet about it is now suing the president of the United States. In the lawsuit, Stormy Daniels claims the hush agreement, as it's called, is invalid because President Trump himself never signed it. The suit also claims the agreement is invalid because President Trump's personal attorney, Michael Cohen, admitted it existed. Here's Daniels' attorney.

(BEGIN VIDEO CLIP)

UNIDENTIFIED FEMALE: Her lawsuit states that she had an intimate relationship with the president. But let's not bother to be delicate. Did she have a sexual relationship with the president?

MICHAEL AVENATTI, ATTORNEY FOR STORMY DANIELS: Yes.

UNIDENTIFIED FEMALE: OK. She also says, according to this document, that there were tangible items, photos, images, that she had them. And according to this agreement, she won't turn them over. She will never release them publicly. Does she still have photos, images, text messages, documents that verify this claim?

AVENATTI: That's a question that Miss Daniels will have to ultimately answer.

Mark, does she have a case? You've read the entire affidavit, the entire document.

MARK O'MARA, CRIMINAL DEFENSE ATTORNEY: What she's doing is asking the court to determine whether or not that contract exists or not. I will tell you that from a pure contract perspective, she's gotten consideration. She took the money. You don't have to have everybody's signature on a contract for it to be enforceable. In effect, Donald Trump, or the "DD" in the contract, is the beneficiary of that contract. But I'm not certain that it's fatal because he didn't sign it. Cohen signed it. Of course she signed it, got the money, and acted in furtherance of that contract. So I'm not -- I don't believe it's fatal simply because Donald Trump didn't sign it.

BLITZER: The other argument they make in this superior court of the state of California document is that since Michael Cohen spoke publicly about the $130,000, he, in effect, was violating the nondisclosure agreement. As a result, the agreement is over. What about that argument?

O'MARA: Probably a stronger argument. The idea that an agreement is out there to say, we will say nothing, and then one party does, can now allow her to counter it.

Again, if we're looking at it like a law school exam question, it's Cohen and Trump who are getting the benefit of the silence. The fact that they violate the benefit that they were given doesn't necessarily open the door wide open for her. But I've got to tell you, a court's going to look at this and say, wait a minute, if you're buying silence, you can't argue against it.

BLITZER: Do people normally get involved in drafting what are called these hush agreements over bogus claims?

O'MARA: Generally speaking, absolutely not. You know, the suggestion that Cohen said it is even false advice or even false information can be detrimental. I understand that. My greatest concern in looking at this whole thing is how any attorney, Cohen or anybody else, sort of acting in a consigleti (ph) role, is going to do something as intense as this, as significant as this, without ever talking to his client. You can't do that. The client, even with giving any type of what we called informed consent, has got to know what's going on. We, as lawyers, cannot take on business occurrences on behalf of a client. I think that's the greatest concern here.

BLITZER: Kate, this is a very lengthy document. I've gone through the whole thing. And, you know, it's official confirmation, at least on the part of Stormy Daniels and her attorney, that there was an affair years earlier between then a private citizen, Donald Trump, and her. How is the first lady going to react when she goes through this?

KATE BENNETT, CNN WHITE HOUSE REPORTER: Probably the same way that she's reacted, which is to be quiet and not make a statement. We've tried to reach out to her office. We have not heard back.

I mean this is a first lady who remains sort of stoic in the face of these -- of these headlines that keep coming up. We've watched her separate herself in some pretty obvious ways, whether it's taking a separate motorcade to meet him at Air Force One and not walk on the South Lawn holding hands, as they do, or, you know, driving separately to State of the Union. Just certain moments that feel as though something is happening inside the White House in the wake of this.

Of course, we have seen her recently, this week, the other day, by the president's side to greet the Netanyahu's. We heard her speak last month for the first time publicly, making public remarks at a luncheon. So -- but as she tries to make these steps forward, here come these Stormy Daniels headlines again, sort of sucking the oxygen out of anything she tries to do. It must be difficult.

[13:25:20] However, she is remaining silent. She has not made a comment so far.

BLITZER: And this -- and, unfortunately for her, and for the president, this story is not going away because there are legal issues now, potentially criminal issues that could be put forward as well.

Kate, thanks very much.

Mark, thanks to you as well.

Other news. He's been off the radar until now. Why George Nader, a Middle East specialist with ties to President Trump, has emerged as a critical piece in the Russia investigation, and what happened when Robert Mueller's team approached him inside an airport as he was landing from overseas.

(COMMERCIAL BREAK)

[13:30:06] BLITZER: He is described as a man of mystery, but a low- profile, Middle East expert is becoming potentially a critical piece in Robert Mueller's investigation.